This invention relates to an active control of automotive induction noise.
Manufacturers have employed active and passive methods to reduce engine noise within the passenger compartment of motor vehicles. Such noise frequently emanates from the engine, travels through the air induction system and emanates out of the mouth of the air intake into the passenger compartment. Efforts have been made to reduce the amount of engine noise traveling through the air induction system. These efforts include the use of both passive devices such as expansion chambers and Helmholtz resonators and active devices involving anti-noise generators.
Active noise attenuation systems use a speaker to create a sound that attenuates engine noise. The sound created is out of phase with the engine noise and combines with the engine noise to result in its reduction. Generally, this sound is generated in proximity to the air induction system. In one such system, the speaker is placed in the mouth of air intake duct.
At low sound frequencies, speakers of current active noise attenuation systems may experience a significant reduction of speaker response. As a consequence, current active noise attenuation systems reduce engine noise less than optimally at these frequencies. Undesirable engine sound may find its way back to the passenger compartment as a consequence.
A need therefore exists to improve speaker response of such systems at low sound frequencies without affecting the effectiveness of the speakers at higher frequencies.
In a disclosed embodiment of this invention, an air induction system comprises an air induction body, a speaker with a first diaphragm disposed about the air induction body, and a second diaphragm spaced from the first diaphragm. A signal, a sound wave, is generated from the first diaphragm and transmitted to the second diaphragm. The second diaphragm generates a noise attenuating sound.
A flow body may interconnect the first diaphragm to the second diaphragm. A tube may be used as the flow body. Further, seals may interconnect the flow body to the first and second diaphragms, creating an inductive mass. This inductive mass serves to improve speaker response at low frequency ranges. While the first diaphragm may be disposed in the air induction body, the second diaphragm may be placed about the mouth of the body. The second diaphragm is preferably flexible. An air filter may also be disposed with the air induction body.
In communication with the speaker is a control unit, which serves to control noise attenuation by the invention. The control unit generates a signal for the speaker with the first diaphragm. The signal is then transmitted to the second diaphragm spaced from the first diaphragm. The signal may be transmitted through a flow body. From the second diaphragm, a noise attenuating sound is created to limit engine noise.
In this way, the invention improves speaker response for noise attenuation systems at a low frequency range without sacrificing speaker response at higher frequencies. Noise attenuation systems are thereby better able to respond to engine noises of low frequency. The improved response is afforded without significant alteration to existing noise attenuation systems. Indeed, the system is easily implemented into existing air induction systems without much additional expense, cost, or labor to install.